In accordance with the prior art the fuel to a process heater is controlled by the final product temperature. This control method corrects for changes in feed stock enthalpy and heating value of the fuel, but only after the final product temperature has been upset. These temperature variations cause upsets in the downstream process, which result in a loss of efficiency and possibly a wide variation in final product quality. Currently used process heater control systems have focused on increased combustion efficiency, however, little attention has been paid to feedforward control to diminish upsets in the temperature of the products leaving a process heater.